Abstract：
Quinone outside inhibitor (QoI) has been applied to manage taro leaf blight caused by Phytophthora colocasiae in southeastern of China for many years. The risk of P. colocasiae to QoI and the potential resistant mechanism remain unknown. In this study, the 74 P. colocasiae strains were sampled from southeastern of China. Sequence analysis of the QoI target Cytb showed one nucleotide variant in the fragment of this gene in this population, producing two haplotypes. The nucleotide variant leads to codon change at 142 (GGT to GCT) producing A142 (alanine) and G142 (glycine) in Hap_1 and Hap_2 strains, respectively. The sensitivity differentiation to azoxystrobin of two haplotypes were observed in vitro. The Hap_1 and Hap_2 strains were confirmed resistant and sensitive by control efficacy of label rate fungicide application, which was 3.0% and 88.8% treated with 500 μg/mL azoxystrobin, respectively. In addition, 10.0 μg/mL azoxystrobin plus 50 μg/mL salicylhydroxamic acid (SHAM) supplemented in PDA medium was identified as a discriminatory dose for differentiation of these two phenotype strains. The azoxystrobin resistant frequency reached 86.5%, indicating prevalence of QoI resistance in the field. Further fitness related features showed that no significant difference in temperature sensitivity, mycelial growth rate, sporangia production, zoospore release and aggressiveness between azoxystrobin-resistant and sensitive strains indicating no potential fitness cost for azoxystrobin resistance. Taken together, azoxystrobin resistance need to be taken into consideration to manage taro leaf blight in southeastern of China.
摘要：
醌外抑制剂（QoI）已在中国东南部应用于防治由疫霉菌引起的芋叶枯病已有多年。大肠杆菌对QoI的风险和潜在的耐药机制仍然未知。在这项研究中,从中国东南部采样了74株。QoI靶标Cytb的序列分析显示该群体中该基因的片段中有一个核苷酸变体，产生两种单倍型。核苷酸变异导致在Hap_1和Hap_2菌株中产生A142（丙氨酸）和G142（甘氨酸）的142（GGT至GCT）密码子改变，分别。在体外观察到两种单倍型对该菌酯的敏感性分化。Hap_1和Hap_2菌株通过标记率杀菌剂施用的控制功效被证实具有抗性和敏感性，用500μg/mL唑酯处理的3.0%和88.8%，分别。此外,将在PDA培养基中补充的10.0μg/mL唑酯和50μg/mL水杨羟胺酸（SHAM）鉴定为区分这两种表型菌株的区分剂量。该菌酯的耐药频率达到86.5%,表明该领域QoI抵抗的患病率。进一步的健身相关特征表明，温度敏感性没有显着差异，菌丝生长速率，孢子囊生产,耐唑菌酯和敏感菌株之间的游动孢子释放和侵袭性表明，耐唑菌酯没有潜在的适应性成本。一起来看,在中国东南部，需要考虑对偶氮酯的抗性，以控制芋叶枯病。
